Sea lions unique adaptation in Galapagos coast

A stounding footage of the Galapagos sea lions hunting was perhaps the highlight of the latest Blue Planet II. For the first time ever, these marine mammals were filmed working as a pack to drive tuna fish in to shallow and rocky waters where they could be caught. The Yellowfin tuna generally possess the ability to swim faster than most predators, except the fastest sharks and the marlins. However,the much slower sea lions were able to outsmart them thanks to an amazing display of movement and co-operation.

The video observed the most fascinating aspect of these creatures, their whiskers. This feature not only makes them great hunters, but enables three of their key adaptations.

Superb sensing

One of the things that can be clearly seen in the footage is just how quickly the sea lions respond to the movements of the fish. They are able to sense exactly where the fish are and react almost instantly, in order to herd them towards the shallow waters.

Sea lions have keen senses that allow them to detect fish, even in murky underwater environments. Similar to other predators, their eyes point forward so that they can easily focus on the prey. They can also open their pupils really wide to let abundant light in, which helps them see clearly underwater.

However, sea lions aren’t always blessed with the clear waters of the Galapagos coastline. In really murky environments, their vision is not good enough. For this reason, sea lions primarily rely on their sense of touch by using their super-sensitive whiskers to feel exactly where the fish are in the water. When the fish swim around they leave little waves, or wakes, behind them. Sea lions are able to detect from these wakes and follow them
through the use of their whiskers.

Most mammals have facial whiskers which, when cut in cross-section, are circular. But, the whiskers of sea lions are uniquely oval. Research has shown that this is the best shape to sense the speed and direction of the wakes, while minimising the vibrating ‘noise’ created by the sea lions own swimming.

At a length of 30 cm, they are the longest whiskers among all mammals. Sea lions can move them backward and forward. They can also sweep their whiskers over objects to feel their size, shape and texture, much like humans use their fingertips. These skills signify that they can find the biggest and tastiest fish, just by touching them with their whiskers.

Sea lions communicate using various ‘barks’ grunts and growls, especially when they are hunting as a group. They have ears that are able to pick up sounds both above and below water. However, their ears are very small, so they can still be super streamlined in water.

Quick moving

This streamlining means that sea lions are able to move quickly and efficiently through the water. Their front flippers are used to push their bodies along, while their back flippers are used for steering. They are able to chase fish at a speed of around 25 mph, but still remain flexible enough to quickly change direction.

Sea lions use their whiskers to guide these fast changes in the desired direction. For example, captive sea lions have learned to balance balls on their noses and are known to move their whiskers ahead of their heads to sense and control the ball. While swimming, they move their whiskers ahead of a full turn in order to constantly scan the space that their head and body are about to move in to. This also means that the whiskers constantly face the direction of the fish that they try to catch.

Clever cognition

Sea lions are extremely clever and display behavioural patterns similar to humans. For instance, they are the only animals that can bob their heads to a musical track. They are also very quick to learn new behaviour, which is why they are common in zoos and aquarium displays.

The footage indeed shows that sea lions are not simply reacting to the fish, but acting out a complex series of well thought out behaviour patterns. Hunting together can increase their chances of making a kill when there are large schools of fish. Usually, sea lions herd the fish in to tight balls. They then hunt them together by picking off the fish from the edges.

They also know that hunting together works only when the prey is abundant,and tend to hunt individually when the prey is scarce. Their whisker-sensing strategies, quick acrobatic movements, and clever cognitive abilities as seen in the footage shows how fantastic they are at hunting speedy fish like tuna.

Source: theconversation